benfb

I would assume that, given the newness of the HS, that it matches the current generation of Prius software. Lexus, for example, is doing a recall on our braking software because it has the same problems as the braking software in the Prius. And Gen 3 is the current Prius, right?

What's involved in installing the SGII? Is that a physical set of gauges that must be wired into the system? Or something virtual that shows up on the Nav screen? I've seen references to it, but I'm not the kind to do DIY kits on my car.

It is interesting to hear your remarks about the coolant temperature because it was about 40 F last night when I drove home. I still don't like the idea of grill blocking, but the other thing that Prius thread discussed was an engine warmer for the morning. That might be worth looking into.

Also, what is DWL (driving with load)?

My house is at higher elevation than downtown (my office), so I get better mileage on average on the way in to work and worse on the way back. I have a choice of a route that involves a lot of 45 mph driving and one that is mostly 35mph driving. The 35 mph route usually has more traffic and, of course, no traffic is best because then I don't have someone tailing gating me when I'm gliding to get the last bit of free speed.

KGenaidy

If I recall correctly about the ABS software ... Lexus says "it's similar" (the programming).

The ScanGaugeII (SGII) plugs into the OBDII port (the "computer port"). It can monitor 4 "gauges" simultaneously. I have mine set right now at instant MPG/RPM/fWT(water temp)/IGN (ignition advance). It's very easy to install and is easily accessable. It is on the dash to the left of instrument cluster. It sits on a sticky pad and is quite stable. The wiring is mostly hidden and out of the way. Here's a link: http://www.scangauge.com/products/ . This tool helps you learn and observe what is really going on with the HSD system.

The idea of Driving with Load (DWL) is that you keep a constant "optimum" load on the engine as opposed to staying at a set speed. So the speed may change but the load on the engine stays constant. The result is better fuel efficiency. However ... this may not be practical with traffic conditions. An example would be driving on the highway and trying to keep the SGII IGN between 18 and 20.

I find 45mph a very difficult speed to get good mpg's at. An idea might be to experiment and try the 45mph route downhill and the 35mph route back. At 45 ... the ICE will always be turning ... so going downhill will help. The other way at 35mph ... there may some opportunities to P&G (pulse and glide) to take advantage of the batteries and EV to improve FE.

benfb

I usually do drive to work (downhill) on route with higher speeds and then home (uphill) on the route with lower speeds. I'm not completely convinced that this makes any difference. The difference is subtle and once you factor in weather, traffic, etc., it's hard to be sure.

For the last two weeks I've been driving in normal mode, not eco mode. I don't see any difference in fuel economy, but the extra power helps with hills and traffic situations. At some point, I'll try the eco mode again and see if that helps. Again, it's hard to be sure because of changing conditions. I'm getting better mileage, but we're having an early spring with temperatures on many days reaching close to 60. So if my mileage goes (by tankful) from 38 to 39 to maybe 40, I assume that's mostly the weather.

Where I get frustrated is the seemingly arbitrary nature of when the system will glide and when it won't. Sometimes the engine is warm (warm weather, driving at least 10 minutes) and the gas engine will insist on running while I'm going downhill. On one recent days, I got gas on my way to work (downhill) and averaged 99.9 gliding all the way. On the way home, the gas ran almost the home time (mostly uphill, but I usually get a fair number of coasting spots) and by the time I got home, the mileage was down to 40+.

What is the point in just running the gas engine when it's warm and the battery is already charged? To improve the air cleanliness? Maybe the programming is tweaked for CA drivers? I'm sure they could do that -- tweak the programming for different driving conditions, such as more stringent air pollution controls or cold or hot climates. And, as I mentioned before, it's upsetting that the car (usually) does so poorly when I have a lot of short trips.

Instead of giving me the eco and power buttons, I wish they have given me some way to tweak the hybrid system. Choose one setting for short trips, where you need maximum efficiency up front. Choose another for longer trips, where you need to maintain efficiency over a longer time or perhaps at higher speeds.

And then I got to thinking that if the Prius can do 50-60 mpg, I'll bet there could be "modes" that would allow an HS to do 50+.

Squirrelsb

The HS is just a heavier car than the Prius and well the body style is entirely different as well. To me, its comparable to the Camry Hybrid (which is what my dad has) in body style and weight and I would expect the mileage to be comparable -- which it is. I have no expectations of Prius or Insight Mileage since those types of cars arent even in the same category as the HS just because its a hybrid. Just like I'm not expecting the RX400h (which I read in forums most folks are struggling to get 30mpg) to get the same mileage as the HS, I have been rather pleased with my HS since I routinely get 35-36mpg on all types of terrain throughout N. Texas and in the city 37-38. 50+ would be nice though!

benfb

I agree that we shouldn't really expect the car to get 50+ mpg and I certainly didn't when I bought it. My current tank of gas is getting about 41 mpg, but we've had an unusually warm March (although my wife just called to say there was brief snow at our house!).

What gets me is that the programming on the HS seems to work against getting the best gas mileage. I'm about to go on several short (1 to 2 miles) trips and I expect that will hurt my mileage. With a hybrid, that shouldn't be a problem, but the programming for the HS is weird. If I could control the car's behavior better, I think I could at least get high 40s in my mileage (assumig good weather).

outbid81

If you know you are taking several short trips, try to plan on driving to the furthest destination and then work your way back. That way the gasoline engine has warmed up to operating temperature on the original trip (less on-time of the gas engine, better fuel economy).

benfb

That's an interesting idea and I might try it sometime. I'm not real sure it will make a difference. It seems tha engine cools down so quickly that if you stop for 45 minutes at each stop, you're pretty much hung no matter what you do. And, naturally, a lot of those short trips aren't in a linear order. The stops are often all over and, of course, the schedule would be the determining factor. If I'm meeting some lawyers at one location, they would expect me there at a certain time, such as 10:00. It wouldn't do for me to go to lunch first (9:00 for lunch?), and that means lunch afterwards. If you're going to a series of stores down a stretch of road, that would make more sense and I will try it. But for random life, it's not going to help.

The other thing is that this is supposed to all be based on when the engine is warm. So why does the engine often insist in running in gas mode when it's definitely warm? Last night I drove home, about a 25 minute drive at speeds 34-45 mph with numerous hills along the way. It was quite cold out (below 40), but that should still have been enough of a drive to warm the engine. I get to my home street with starts with a large, steep hill (an unpleasant bike ride, that's for sure) and then ends with a level stretch to my driveway. Once I reach the top of the hill, the engine refused to go into hybrid mode, even if I tried stopping. In fact, all the rest of the way to my garage I averaged around 15 mpg, even though I glided downhill and then gently drove on level ground. It should have been 90 mpg; but it insisted on running that gas motor.

So there is some more complicated determining factor than just engine temperature involved, although warmer weather definitely helps. I just don't know the algorithm and I suspect that the programming is hurting more than helping.

Actually, now that I think about it, I could say that last night I experience "runaway gas consumption", comparable to the current publicized problem of runaway acceleration.

KGenaidy

That's the S3 to S4 "mode" transition point that is exposing itself. The only way for the transition to complete is to be stopped and the engine will continue to run for 7-10 seconds. It took me a few months to understand what this behavior is and to be able to logically explain it. There is a minimum coolant temp required for this behavior to expose itself ... it appears to be somewhere around 165 degrees.

benfb

It seems to me the coolant temp should already be pretty high by the time I get home. My typical drive home at the end of the day is 20-30 minutes. It always ends with a drive up a very steep hill and then back down the other side, and then a short flat stretch. Most of the time (but not always), when I get to the top of that hill, the engine won't stop running, even if I stop the car for 10 seconds. After that much work, the engine has to be quite warm and, as I said, the stopping trick doesn't work. Sometimes, however, it just magically goes into glide mode. I haven't been able to find any reason for one behavior over another, but I dont' see how it could be coolant temp.

outbid81

Keep in mind that an Atkinson cycle engine is most effective with steady throttle and about 2000rpm. At optimal temps, this is a perfect time for the gas engine to run.

benfb

I would anticipate that if the goal is to run the electric engine as much as possible, then you're not always going to get optimal performance out of the gas engine. Especially in the case of short trips, what is the point of warming the gas engine to optimal performance if you only reach that temperature at the point when you're stopping?

I made another one of those many-stops trips today: office to lunch to bank to FedEx to office. Each leg was a mile or two at the most. Each stop was minimum 1/2 hour. Weather was 45 and raining. The average mileage during this trip was about 20 mpg or a little less.

I don't even bother with the Eco mode any more, since it's useless if you drive right anyway. However, if someone changed the Eco mode into "short distances", that would be useful. Then for those 1 mile trips, I would turn on Eco mode and the system would know to not worry about optimal performance from the gas engine. On longer trips, I leave off the Eco mode and the system can do what it does now.

Of course, none of this explains that bizarre behavior where the gas engine insists on staying on after climbing the hill near my home. The engine is already warmed up and it's ridiculous to get 20 mpg (or worse) while coasting downhill!

I would love to get into a technical discussion with a systems engineer and a programmer from Toyota/Lexus. I have a background in both those fields (although not related to the automotive industry!) and I can see signs that someone set their priorities based on bad assumptions about the real world.

KGenaidy

Hi benfb,

I'm guessing the goal is to get the best fuel economy with the hybrid system over a wide range of driving conditions. This includes both the gas engine and the electric engine. Hybrids are at their worst in what the driving conditions you describe and encounter (short trips). It wouldn't matter if it was either a Toyota or a Honda based implementation of their hybrid systems.

What Eco mode gives you that isn't as available ... or not at all in the other modes (Normal/Power) ... is the most ability to control the way the HSD will work. The trade off for this is that it seems "sluggish". Yes ... I absolutely agree that the accelerator requires more movement to respond. However ... it is this very behavior that gives an additional measure of control over the HSD system.

The S3-S4 transition point is "weird". My best advise (if possible given conditions) is to force the transition on your terms as early as possible. If you get into the situation where the computer is trying to do it as you have described ... the only way out (read have the transition happen), is come to a stop and force the transition (read either wait as long as it takes (took about 20 sec yesterday for me) to shut off ... or force it via the "blipping" to restart the gas engine and wait for shutoff). Otherwise ... this "cycle" will continue to happen as the computer sees fit.

20mpg downhill gliding with a cold vehicle (read first 3-5 minutes) is quite possible. After that ... it's all about how the HSD is driven. My expectation and experience is to be pulling at least 60+ mpg. To get that though ... I have had to learn how to make the HS do what I want.

When I started driving hybrids ... I made a choice to learn how to drive them efficiently. I have found that this has not been as easy as it sounds. I still consider myself a novice after about 1 1/2 years. On the other hand, it has made my driving much more "fun" due to the mental stimulation and challenges.

benfb

I haven't visited here for a while, but I've continued to test my car and make observations. I love my car, but the inconsistent/illogical behavior of the hybrid system is frustrating. If I ignored the mileage and just focused on the ride, I'd probably be happy. But I like to see how I can manage the mileage and the car's behavior is soooo frustrating.

First, the car always needs to warm up before allowing EV mode. That makes EV mode useless for the advertised purpose of parking lots.

Second, if the car has to work hard going up a steep hill, then the gas motor continues to run on the downhill side, even if I'm just coasting. That is inherently inefficient.

Third, there are many times when the car is ready to go into S4 mode, but the only way to cause it is to pull over and let the car idle for 45 seconds. It would be really useful to have a way to boot the car into S4 while you're still driving.

I have observed that the car does better now that warm weather has arrived, but it still seems really inefficient. So, has anyone had any new insights or heard anything?

KGenaidy

Hi Benfb,

Yes ... the car does need to warm up before EV is available. I don't use pure EV until the end of my commute so I can't really tell you exactly when it becomes available.

If the HS is going over about 40-42 mph ... the engine will always turn. This does not mean though that fuel will always be flowing to cylinders. From http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive There is a "safe" maximum rpm for one of the 2 motors and it is reached at the 40-42 mph range. More information on this can be found here: http://eahart.com/prius/psd/

Getting into S4 is dependent on the coolant temp being at least 160F degrees. Without a SG2 or similar device .... I'm not sure how you would really know if it's ready to transition or not. Actually I have you to thank for this .. this thread is what helped me be able to quantify and articulate the behavior.

Getting to the "next level" with the HS might require an investment in a Scanguage II (SG2). It really does help take the guess work out of what is going on. Mine has been invaluable to me to understand the way the hybrid systems work.

I purchased my HS in 10/2009 and now have 10k miles on it with a life to date 45.102 mpg. Without the SG2 ... I'm positive my fuel efficiency would have been significantly lower.

benfb

Thanks for the information on the HSD, although I'm not sure exactly how that helps me manage my mileage. I'm impressed that you're still getting 45 mpg. I once got 99.9 mpg over six miles on a new tank of gas, does that count? The best I have done on any single tank of gas is 41.0 mpg and my average in five months of owning the car is 38.3 mpg.

I know about the 41 mph limit on the S4 mode. I often take routes that let me drive at 35-40 mpg instead of 45 mpg, so I can glide instead of guzzle. The last three miles on my way home (or on my way out in the morning) are on a 45 limit road where most cars go 50. I try to go 40 when no one is around, but I don't have that luxury when there's traffic.

You've talked about the coolant temperature before. I really don't want to get into an additional gauge and it should be possible to tell when the coolant is warm if I've been driving for a while in gas mode. However, there are times when it refuses to go into (or drops out of) glide mode even when the engine is quite warm. A typical scenario: I've drive for at least five minutes in gas mode at 45 mpg and the car is finally in S4 mode. Then I hit a spot where I have to accelerate, forcing it out of S4. Once I coast again, it refuses to go back into S4.

If it's strictly a matter of coolant temperature, then why do we need to pull over and idle for 45 second to go into S4? I am often in situations where I know the coolant is hot, the battery is charged, and my speed is low and yet it refuses to go into S4. If I pull over and wait, it will switch to electric mode, but that would mean the coolant temperature dropping, not rising. There are times where I've been stuck driving for miles in gas mode because it's impractical (no time or no space) to pull over, even though that would give me S4 if I did.

None of this explains the gas engine's need to keep running after a strong acceleration, such as climbing a steep hill. The engine works a lot harder, so I would expect the coolant temperature to rise. Yet once I crest that hill, the car will continue to get poor mileage all the way down the other side.

Finally, did you note the post from the guy with the LS hybrid who says his car can go straight into electric mode on start up? My wife's 2006 400h is the same -- she can go straight into electric at low speeds from start up. So if they can do it, why can't we? What purpose is served by forcing our gas engines to heat up first?

I've thought a lot about your posts because you provided such excellent information. Yet I still find nothing to explain my car's behavior. I also thought about the fact that you have averaged 45 mpg. It would be impossible for my car to get that kind of average on a level road (or even a slight downhill), even in warm temperatures.